U.S. patent application number 14/913662 was filed with the patent office on 2017-06-08 for controlling access to a shared wireless medium in a wireless communication system.
The applicant listed for this patent is TELEFONAKTIEBOLAGET LM ERICSSON (PUBL). Invention is credited to Christofer Lindheimer, Johan Soder, Leif Wilhelmsson.
Application Number | 20170164403 14/913662 |
Document ID | / |
Family ID | 55398355 |
Filed Date | 2017-06-08 |
United States Patent
Application |
20170164403 |
Kind Code |
A1 |
Lindheimer; Christofer ; et
al. |
June 8, 2017 |
Controlling Access to a Shared Wireless Medium in a Wireless
Communication System
Abstract
There is provided a method of controlling access to a shared
wireless medium in a first wireless communication system based on a
contention-based protocol for medium access involving carrier
sensing, wherein the first wireless communication system is of a
first radio access technology. The method comprises determining
(S1) whether a second wireless communication system of a second,
different radio access technology is operating on the same channel
of the shared wireless medium as the first wireless communication
system. The method also comprises initiating (S2), if the second
wireless communication system is operating on the same channel, a
change of a carrier-sensing threshold used in the first wireless
communication system for determining, for at least one
communication unit, whether the medium is available for access from
a first level to a second, different level.
Inventors: |
Lindheimer; Christofer;
(Linkoping, SE) ; Soder; Johan; (Stockholm,
SE) ; Wilhelmsson; Leif; (Dalby, SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TELEFONAKTIEBOLAGET LM ERICSSON (PUBL) |
Stockholm |
|
SE |
|
|
Family ID: |
55398355 |
Appl. No.: |
14/913662 |
Filed: |
January 15, 2016 |
PCT Filed: |
January 15, 2016 |
PCT NO: |
PCT/SE2016/050017 |
371 Date: |
February 22, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62194735 |
Jul 20, 2015 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 67/14 20130101;
H04L 29/08576 20130101; H04W 74/0825 20130101; H04W 74/04 20130101;
H04W 74/0816 20130101; H04W 74/085 20130101; H04W 74/08
20130101 |
International
Class: |
H04W 74/04 20060101
H04W074/04; H04L 29/08 20060101 H04L029/08; H04W 74/08 20060101
H04W074/08 |
Claims
1-33. (canceled)
34. A method of controlling access to a shared wireless medium in a
first wireless communication system based on a contention-based
protocol for medium access involving carrier sensing, wherein the
first wireless communication system is of a first radio access
technology, the method comprising: determining whether a second
wireless communication system of a second, different, radio access
technology is operating on the same channel of the shared wireless
medium as the first wireless communication system; and initiating,
in response to determining that the second wireless communication
system is operating on the same channel, a change of a
carrier-sensing threshold used in the first wireless communication
system for determining, for at least one communication unit,
whether the medium is available for access, from a first level to a
second, different level.
35. The method of claim 34, wherein the carrier-sensing threshold
is increased from a first lower level to a second, higher,
level.
36. The method of claim 34, wherein the first threshold level is
used for carrier-sensing applicable for transmissions originating
from the same service set, whereas the second threshold level is
used for carrier-sensing applicable for transmissions originating
from other service sets within the first wireless communication
system.
37. The method of claim 34, wherein the carrier-sensing threshold
is aligned to a so-called co-existence threshold level which
differs from a default carrier-sensing threshold level used for
signal detection within the first wireless communication
system.
38. The method of claim 37, wherein the default carrier-sensing
threshold level is maintained for carrier-sensing applicable for
transmissions originating from within the same service set.
39. The method of claim 37, wherein the co-existence level
corresponds to one of: the level of a threshold used in the second
wireless communication system for determining whether the medium is
available for access; the level used in the first wireless
communication system for determining whether the medium is
available for access when no carrier is detected; and the level
used in the first wireless communication system for energy
detection.
40. The method of claim 34, wherein the carrier-sensing threshold
is a threshold for detection of signals, involving at least
partially decoding and/or otherwise recognizing a certain type of
signals, within the first wireless communication system.
41. The method of claim 34, wherein the carrier-sensing threshold
is a Clear Channel Assessment Threshold (CCAT).
42. The method of claim 34, wherein a first carrier-sensing
threshold is assigned for use in the first wireless communication
system, applicable for transmissions identified as originating from
within the same service set as the carrier-sensing communication
unit, and a second carrier-sensing threshold is assigned for use in
the first wireless communication system, applicable for
transmissions identified as originating from outside the service
set of the carrier-sensing communication unit, wherein the second
carrier-sensing threshold is aligned or changed to the second
level.
43. The method of claim 34, wherein the step of determining whether
a second wireless communication system of a second, different type
or radio access technology is operating on the same channel of the
shared wireless medium as the first wireless communication system
includes identifying ongoing or recent transmissions in the second
wireless communication system on the considered channel.
44. The method of claim 34, wherein the first wireless
communication system is a Wireless Local Area Network (WLAN) system
and the second wireless communication system is a cellular radio
network operating in unlicensed spectrum.
45. The method of claim 44, wherein the first wireless
communication system is a Wi-Fi system.
46. The method of claim 44, wherein the second wireless
communication system is based on License Assisted Access (LAA) or
Long Term Evolution (LTE)-unlicensed.
47. The method of claim 34, wherein the method is performed by a
communication unit of the first wireless communication system.
48. The method of claim 47, wherein the communication unit is an
access point or a wireless communication device.
49. The method of claim 34, wherein an access point initiates the
change of the carrier-sensing threshold by informing at least one
associated wireless communication device that the carrier-sensing
threshold should be changed from the first level to the second
level.
50. The method of claim 34, wherein a wireless communication device
identifies that the second wireless communication system is
operating on the same channel as the first wireless communication
system and initiates the change of the carrier-sensing
threshold.
51. A network node configured to control access to a shared
wireless medium in a first wireless communication system based on a
contention-based protocol for medium access involving carrier
sensing, wherein the first wireless communication system is of a
first radio access technology, the network node comprising a
processing circuit configured to: determine whether a second
wireless communication system of a second, different radio access
technology is operating on the same channel of the shared wireless
medium as the first wireless communication system; and initiate, in
response to determining that the second wireless communication
system is operating on the same channel, a change of a
carrier-sensing threshold used in the first wireless communication
system for determining, for at least one communication unit,
whether the medium is available for access, from a first level to a
second, different level.
52. The network node of claim 51, wherein the carrier-sensing
threshold is increased from a first lower level to a second higher
level.
53. The network node of claim 51, wherein the carrier-sensing
threshold is aligned to a so-called co-existence threshold level
which differs from a default carrier-sensing threshold level used
for signal detection within the first wireless communication
system.
54. The network node of claim 53, wherein the default
carrier-sensing threshold level is maintained for carrier-sensing
applicable for transmissions originating from users within the same
service set.
55. The network node of claim 53, wherein the co-existence level
corresponds to the level of a threshold used in the second wireless
communication system for determining whether the medium is
available for access, or wherein the co-existence level corresponds
to the level used in the first wireless communication system for
determining whether the medium is available for access when no
carrier is detected, or wherein the co-existence level corresponds
to the level used in the first wireless communication system for
energy detection.
56. The network node of claim 51, wherein the carrier-sensing
threshold is a threshold for detection of signals within the first
wireless communication system.
57. The network node of claim 51, wherein the first wireless
communication system is a Wireless Local Area Network (WLAN) system
and the second wireless communication system is a cellular radio
network operating in unlicensed spectrum.
58. The network node of claim 57, wherein the first wireless
communication system is a Wi-Fi system.
59. The network node of claim 57, wherein the second wireless
communication system is based on License Assisted Access (LAA) or
Long Term Evolution (LTE)-unlicensed.
60. The network node of claim 51, wherein the network node is an
access point, radio network node or access controller.
61. A computer-readable medium comprising, stored thereupon, a
computer program for controlling, when executed by at least one
processor, access to a shared wireless medium in a first wireless
communication system based on a contention-based protocol for
medium access involving carrier sensing, wherein the first wireless
communication system is of a first radio access technology, wherein
the computer program comprises instructions, which when executed,
cause the at least one processor to: determine whether a second
wireless communication system of a second, different radio access
technology is operating on the same channel of the shared wireless
medium as the first wireless communication system; and initiate, in
response to determining that the second wireless communication
system is operating on the same channel, a change of a
carrier-sensing threshold used in the first wireless communication
system for determining, for at least one communication unit,
whether the medium is available for access from a first level to a
second, different level.
Description
TECHNICAL FIELD
[0001] The proposed technology generally relates to wireless
communication technology, and more specifically methods and
arrangements for controlling access to a shared wireless medium
based on a contention-based protocol for medium access involving
carrier sensing, and corresponding communication units, computer
programs and computer-program products and apparatuses.
BACKGROUND
[0002] In general, medium access is of outmost importance for the
operation and performance of communication networks.
[0003] A contention-based protocol is a communication protocol for
medium access and for operating communication equipment that allows
many users to use the same transmission medium such as a radio
medium with little or no pre-coordination.
[0004] Carrier Sensing, CS, and Listen Before Talk, LBT, are
examples of contention-based procedures for medium access used in
wireless communications whereby a radio transmitter first senses
its radio environment, i.e. the shared wireless medium or (radio)
channel, before it starts a transmission. Sometimes Listen Before
Talk is referred to as Sense Before Transmit. The LBT operating
procedure in IEEE 802.11 for Wireless Local Area Networks, WLANs,
is one of the most well-known contention-based protocols.
[0005] For example, Carrier Sensing Multiple Access, CSMA, is a
Medium Access Control, MAC, protocol in which a node verifies the
absence of other traffic before transmitting on a shared
transmission medium, such as an electrical bus, or a band of the
electromagnetic spectrum.
[0006] Carrier Sensing generally means that a transmitter uses
feedback from a receiver to determine whether another transmission
is in progress before initiating a transmission. That is, the
transmitter tries to detect the presence of a transmission or
carrier wave from another station before attempting to transmit. If
a transmission/carrier is sensed, the station waits for the
transmission in progress to finish before initiating its own
transmission. Multiple access means that multiple stations send
and/or receive on the medium.
[0007] FIG. 1 is a schematic diagram illustrating an example of a
wireless network employing carrier sensing with a so-called Clear
Channel Assessment Threshold, CCAT. Each access point, AP, normally
has a CCAT and a corresponding sensing area. Sensing area can here
be understood as the area in which a transmission will be declared
as present. The CCAT is used by the AP when performing carrier
sensing for transmissions to any of the portable terminals,
commonly referred to as stations, STAs, associated to the AP.
Similarly, each STA normally also has a CCAT for carrier sensing
for transmissions to the AP.
[0008] However, wireless networks using carrier sensing as a basis
for medium access typically suffer from low spectral efficiency
and/or low spatial reuse in dense deployments. This is due to the
fact that STAs and APs must defer from accessing the wireless
medium if they sense that the medium is busy. To increase the
spatial reuse, the medium sensing thresholds may be tuned to be
more aggressive. However, this may lead to high interference
situations, leading to reduced system performance and impaired user
experience.
[0009] It has also been recognized that traditional
contention-based protocols for medium access suffers from various
problems, e.g. relating to unbalanced and/or unfair medium or
channel sharing between different communication stations and/or
different types of communication systems.
[0010] In particular, different types of communication systems may
use different strategies and/or thresholds for medium access, which
may lead to such an unbalanced and/or unfair medium or channel
sharing.
SUMMARY
[0011] It is an object to provide an efficient way of controlling
access to a shared wireless medium. By way of example, it is
desirable to improve the coexistence of different types of wireless
communication systems, especially when operating in unlicensed
spectrum.
[0012] It is a specific object to provide a method of controlling
access to a shared wireless medium.
[0013] It is also an object to provide an arrangement configured to
control access to a shared wireless medium.
[0014] Another object is to provide a communication unit comprising
such an arrangement.
[0015] Yet another object is to provide a computer program for
controlling, when executed by at least one processor, access to a
shared wireless medium.
[0016] Still another is to provide a computer-program product
comprising a computer-readable medium having stored thereon such a
computer program.
[0017] It is also an object to provide an apparatus for controlling
access to a shared wireless medium.
[0018] These and other objects are met by embodiments of the
proposed technology.
[0019] According to a first aspect, there is provided a method of
controlling access to a shared wireless medium in a first wireless
communication system based on a contention-based protocol for
medium access involving carrier sensing, wherein the first wireless
communication system is of a first radio access technology. The
method comprises: [0020] determining whether a second wireless
communication system of a second, different radio access technology
is operating on the same channel of the shared wireless medium as
the first wireless communication system; and [0021] initiating, if
the second wireless communication system is operating on the same
channel, a change of a carrier-sensing threshold used in the first
wireless communication system for determining, for at least one
communication unit, whether the medium is available for access from
a first level to a second, different level.
[0022] According to another aspect, there is provided an
arrangement configured to control access to a shared wireless
medium in a first wireless communication system based on a
contention-based protocol for medium access involving carrier
sensing, wherein the first wireless communication system is of a
first radio access technology. The arrangement is configured to
determine whether a second wireless communication system of a
second, different radio access technology is operating on the same
channel of the shared wireless medium as the first wireless
communication system. The arrangement is also configured to
initiate, if the second wireless communication system is operating
on the same channel, a change of a carrier-sensing threshold used
in the first wireless communication system for determining, for at
least one communication unit, whether the medium is available for
access from a first level to a second, different level.
[0023] According to yet another aspect, there is provided a
communication unit comprising an arrangement as described
herein.
[0024] According to still another aspect, there is provided a
computer program for controlling, when executed by at least one
processor, access to a shared wireless medium in a first wireless
communication system based on a contention-based protocol for
medium access involving carrier sensing, wherein the first wireless
communication system is of a first radio access technology. The
computer program comprises instructions, which when executed, cause
the at least one processor to: [0025] determine whether a second
wireless communication system of a second, different radio access
technology is operating on the same channel of the shared wireless
medium as the first wireless communication system; and [0026]
initiate, if the second wireless communication system is operating
on the same channel, a change of a carrier-sensing threshold used
in the first wireless communication system for determining, for at
least one communication unit, whether the medium is available for
access from a first level to a second, different level.
[0027] According to another aspect, there is provided a
computer-program product comprising a computer-readable medium
having stored thereon a computer program as defined herein.
[0028] According to yet another aspect, there is provided an
apparatus for controlling access to a shared wireless medium in a
first wireless communication system based on a contention-based
protocol for medium access involving carrier sensing, wherein the
first wireless communication system is of a first radio access
technology. The apparatus comprises: [0029] a determining module
for determining whether a second wireless communication system of a
second, different radio access technology is operating on the same
channel of the shared wireless medium as the first wireless
communication system; and [0030] a control module for initiating,
if the second wireless communication system is operating on the
same channel, a change of a carrier-sensing threshold used in the
first wireless communication system for determining, for at least
one communication unit, whether the medium is available for access
from a first level to a second, different level.
[0031] An advantage of the proposed technology is a more efficient
strategy for controlling access to a shared wireless medium and
especially a more fair and/or balanced medium or channel sharing
between different communication stations and/or different types of
wireless communication systems.
[0032] Other advantages will be appreciated when reading the
detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] The embodiments, together with further objects and
advantages thereof, may best be understood by making reference to
the following description taken together with the accompanying
drawings, in which:
[0034] FIG. 1 is a schematic diagram illustrating an example of a
wireless network employing carrier sensing with a common Clear
Channel Assessment Threshold, CCAT.
[0035] FIG. 2 is a schematic flow diagram illustrating an example
of a method of controlling access to a shared wireless medium
according to an embodiment.
[0036] FIG. 3 is a schematic flow diagram illustrating an example
of a method for carrier sensing in a wireless communication system
according to an embodiment.
[0037] FIG. 4 is a schematic diagram illustrating an example of two
WLAN access points taking turn in accessing a radio communication
channel.
[0038] FIG. 5 is a schematic diagram illustrating an example of two
WLAN access points and a base station or similar network node of
another type of wireless communication system competing for access
to a radio communication channel.
[0039] FIG. 6 is a schematic block diagram illustrating an example
of an arrangement according to an embodiment.
[0040] FIG. 7 is a schematic diagram illustrating an example of a
communication unit comprising an arrangement of FIG. 6.
[0041] FIG. 8 is a schematic diagram illustrating an example of a
computer implementation according to an embodiment.
[0042] FIG. 9 is a schematic diagram illustrating an example of an
apparatus for controlling access to a shared wireless medium in a
wireless communication system according to an embodiment.
[0043] FIG. 10 is a schematic diagram illustrating an example of an
apparatus for threshold assignment for carrier sensing in a
wireless communication system according to an embodiment.
[0044] FIG. 11A is a schematic diagram illustrating an example of
communication units of different types of communication systems
using different strategies and/or thresholds for medium access.
[0045] FIG. 11B is a schematic diagram illustrating an example of
the received signal level originating from an access point and the
relation to a COAT threshold and energy detect threshold.
DETAILED DESCRIPTION
[0046] Throughout the drawings, the same reference designations are
used for similar or corresponding elements.
[0047] As used herein, the non-limiting term "network node" may
refer to an access point or similar radio network node including
also access controllers and the like.
[0048] As used herein, the non-limiting terms "wireless
communication device" and "wireless device" may refer to a terminal
or station, STA, User Equipment, UE, a mobile phone, a cellular
phone, a Personal Digital Assistant, PDA, equipped with radio
communication capabilities, a smart phone, a laptop or Personal
Computer, PC, equipped with an internal or external mobile
broadband modem, a tablet PC with radio communication capabilities,
a target device, a device to device UE, a machine type UE or UE
capable of machine to machine communication, iPad, customer
premises equipment, CPE, laptop embedded equipment, LEE, laptop
mounted equipment, LME, USB dongle, a portable electronic radio
communication device, a sensor device equipped with radio
communication capabilities or the like. In particular, the term
"wireless device" should be interpreted as a non-limiting term
comprising any type of wireless device communicating with a radio
network node in a wireless communication system or any device
equipped with radio circuitry for wireless communication according
to any relevant standard for wireless communication.
[0049] In the following, the general non-limiting term
"communication unit" includes network nodes and/or associated
wireless devices.
[0050] For a better understanding it may be useful to begin with a
brief overview and problem analysis.
[0051] As mentioned, different types of communication systems may
use different strategies and/or thresholds for medium access, which
may lead to unbalanced and/or unfair medium or channel sharing.
[0052] For example, cellular radio access technologies such as
License Assisted Access, LAA, or Long Term Evolution Unlicensed,
LTE-U, are being introduced in the unlicensed spectrum such as the
5 GHz band and will co-exist together with other wireless networks
such as WLANs, e.g. Wi-Fi. LAA is a technology for aggregated
access to licensed and unlicensed spectrum, and allows operators to
benefit from the additional capacity available in the unlicensed
part of the spectrum.
[0053] Wi-Fi uses a carrier sensing mechanism to assess if the
channel is busy prior to transmission. If the channel is sensed as
busy, Wi-Fi will defer transmissions and sense again.
[0054] The same principles are being discussed for LAA, and there
is currently an ongoing discussion how these mechanisms should
work.
[0055] To assess if the medium or channel is busy, Wi-Fi uses a
Clear Channel Assessment Threshold, CCAT, for which, if a received
Wi-Fi signal is stronger than this level, the channel is perceived
as occupied. If the signal is not stronger than this threshold, the
channel is perceived as idle, and it is OK to transmit. This
procedure is denoted signal detection (also referred to as
pre-amble detection). Signal detection is conditioned on the
possibility to actually identify a Wi-Fi signal, i.e., actually
decode parts of a packet. If it is not possible to decode a Wi-Fi
signal, a procedure referred to as energy detection is used
instead. In energy detection the received energy level is measured
and compared to another threshold, the energy detect threshold,
which is 20 dB higher than the COAT.
[0056] LAA also uses a threshold, but does not attempt to t detect
any Wi-Fi signal. It simply use the energy detect threshold, i.e.,
the same higher threshold for when "any energy" is detected, to
assess if the channel is busy.
[0057] The inventors have recognized that in some scenarios it may
be detrimental to Wi-Fi if it uses a different threshold than LAA
or LTE-unlicensed for assessing when a channel is available.
[0058] FIG. 11A is a schematic diagram illustrating an example of
communication units of different types of communication systems
using different strategies and/or thresholds for medium access. In
this example, Wi-Fi access points AP1 and AP2 employ a COAT
threshold to assess if the medium or channel is busy. A co-existing
eNB on the other hand may simply use the energy detect threshold to
assess if the channel is busy.
[0059] This may render that, everything else equal, LAA or
LTE-unlicensed users may obtain much more transmission
opportunities than any Wi-Fi user, whether STA or AP.
[0060] FIG. 11B is a schematic diagram illustrating an example of
the received signal level originating from an access point, AP2,
and the relation to a COAT threshold and energy detect threshold.
Assuming the same or similar signal level is received by eNB and
AP1, the eNB may assess the medium as free while AP1 will assess
the medium as busy because the eNB uses the higher energy detect
threshold and AP1 uses the lower COAT threshold.
[0061] Specifically, two or more Wi-Fi networks using the same
channel may thus not be able operate simultaneously due to that the
COAT is set to -82 dBm, whereas if LAA or LTE-unlicensed is
operating in the same channel this may be able to work concurrently
with the Wi-Fi networks. Effectively this means that in deployments
where there are already Wi-Fi networks, it may be the case that
Wi-Fi has a slight disadvantage compared to LAA or LTE-unlicensed
when doing network densification.
[0062] FIG. 2 is a schematic flow diagram illustrating an example
of a method of controlling access to a shared wireless medium
according to an embodiment.
[0063] According to a first aspect, there is provided a method of
controlling access to a shared wireless medium in a first wireless
communication system based on a contention-based protocol for
medium access involving carrier sensing, wherein the first wireless
communication system is of a first radio access technology. The
method comprises: [0064] S1: determining whether a second wireless
communication system of a second, different radio access technology
is operating on the same channel of the shared wireless medium as
the first wireless communication system; and [0065] S2: initiating,
if the second wireless communication system is operating on the
same channel, a change of a carrier-sensing threshold used in the
first wireless communication system for determining, for at least
one communication unit, whether the medium is available for access
from a first level to a second, different level.
[0066] In this way, a more fair and/or balanced medium or channel
sharing between different communication stations and/or different
types of communication systems may be obtained.
[0067] By way of example, the carrier-sensing threshold used in the
first wireless communication system for determining, for at least
one communication unit, whether the medium is available for access
is increased from a first lower level to a second higher level.
[0068] As a possible add-on, the first threshold level may be used
for carrier-sensing applicable for transmissions originating from
the same service set, whereas the second threshold level may be
used for carrier-sensing applicable for transmissions originating
from other service sets within the first wireless communication
system. The second threshold level may thus be used for
carrier-sensing for transmissions originating from other service
sets under the condition that it has been determined that the
second wireless communication system is operating on the same
channel of the shared wireless medium as the first wireless
communication system.
[0069] For example, the carrier-sensing threshold used in the first
wireless communication system for determining, for at least one
communication unit, whether the medium is available for access may
be aligned to a so-called co-existence threshold level which
differs from a default carrier-sensing threshold level used for
signal detection within the first wireless communication
system.
[0070] In a particular example, the default carrier-sensing
threshold level is nevertheless maintained for carrier-sensing
applicable for transmissions originating from within the same
service set.
[0071] A service set is normally considered as a set of
communication units or devices associated with a wireless network,
and especially a WLAN type network. In particular, a Basic Service
Set, BSS, provides the basic building block of a WLAN such as
802.11 type wireless network. In infrastructure mode, an access
point together with associated stations, STAs, is called a BSS.
Alternatively, it is possible to set up an ad hoc network of client
stations without a controlling access point, the result is normally
called and Independent Basic Service Set, IBSS. An Extended Service
Set, ESS, is a set of two or more interconnected BSSs that share
the same Service Set Identification, SSID.
[0072] In a particular embodiment, a first carrier-sensing
threshold is assigned for use in the first wireless communication
system, applicable for transmissions identified as originating from
within the same service set as the carrier-sensing communication
unit. A second carrier-sensing threshold is assigned for use in the
first wireless communication system, applicable for transmissions
identified as originating from outside the service set of the
carrier-sensing communication unit, wherein the second
carrier-sensing threshold is aligned or changed to the second
level.
[0073] Typically, the co-existence threshold level corresponds to a
situation of co-existence of transmissions of the first wireless
communication system and the second wireless communication system
on the same channel.
[0074] As an example, the co-existence threshold level is higher
than the default carrier-sensing threshold level.
[0075] In a particular embodiment, the co-existence level
corresponds to the level of a threshold used in the second wireless
communication system for determining whether the medium is
available for access.
[0076] By way of example, the co-existence level may correspond to
the level used in the first wireless communication system for
determining whether the medium is available for access when no
carrier is detected.
[0077] The co-existence level may correspond to the level used in
the first wireless communication system for energy detection.
[0078] As an example, the carrier-sensing threshold is a threshold
for detection of signals within the first wireless communication
system. This may involve at least partially decoding and/or
otherwise recognizing a certain type of signals, e.g. WLAN or Wi-Fi
signals.
[0079] The carrier-sensing threshold may be a Clear Channel
Assessment Threshold, CCAT.
[0080] In a particular embodiment, the step of determining whether
a second wireless communication system of a second, different type
or radio access technology is operating on the same channel of the
shared wireless medium as the first wireless communication system
includes identifying ongoing or recent transmissions in the second
wireless communication system on the considered channel.
[0081] By way of example, the first wireless communication system
may be a Wireless Local Area Network, WLAN, system and the second
wireless communication system may be a cellular radio network
operating in unlicensed spectrum.
[0082] For example, the first wireless communication system may be
a Wi-Fi system.
[0083] For example, the second wireless communication system may be
based on License Assisted Access, LAA, or Long Term Evolution, LTE,
unlicensed.
[0084] The method may for example be performed by a communication
unit such as an access point or wireless communication device of
the first wireless communication system.
[0085] By way of example, an access point may initiate the change
of the carrier-sensing threshold by informing at least one
associated wireless communication device that the carrier-sensing
threshold should be changed from the first level to the second
level. For example, an access point may inform the associated STAs
of its BSS of the change of carrier-sensing threshold through an
information bit or information field in the beacon broadcast
transmission. As another example an access point may inform each
associated STAs of the same BSS by means of unicast information of
a dedicated signaling message. As yet another example an access
point may inform associated STAs of the same BSS by setting an
information bit of a header when data is transmitted (DL or UL)
between the access point and the station. If data is transmitted in
the UL direction, the information may be conveyed in the ACK frame
sent by the access point. If the data is transmitted in the DL
direction, the information may be conveyed in the PHY or MAC header
of the data transmission.
[0086] Alternatively, a wireless communication device may identify
that the second wireless communication system is operating on the
same channel as the first wireless communication system and
initiate the change of the carrier-sensing threshold.
[0087] FIG. 3 is a schematic flow diagram illustrating an example
of a method for carrier sensing in a wireless communication system
according to an embodiment. This method could possibly be used
independently, but is preferably used as an add-on to the
previously described method according to the first aspect, when
another system of a different radio access technology has been
detected.
[0088] There is thus provided a method for carrier sensing by a
communication unit in a first wireless communication system,
wherein the communication unit belongs to a service set.
[0089] The method comprises: [0090] S11: assigning a first
carrier-sensing threshold for use in the first wireless
communication system, applicable for transmissions identified as
originating from within the same service set; and [0091] S12:
assigning a second carrier-sensing threshold for use in the first
wireless communication system, applicable for transmissions
identified as originating from other service sets, [0092] wherein
the first carrier-sensing threshold and the second carrier-sensing
threshold are different.
[0093] In other words, for carrier-sensing by a particular
communication unit such as an access point or an associated
wireless communication device, there is a distinction between
transmissions identified as originating from within the same
service set as the considered communication unit and transmissions
identified as originating from other service sets.
[0094] In particular, this means that the first carrier-sensing
threshold may be applied when detecting signals to/from
communication units within the service set to which the
carrier-sensing communication unit belongs, whereas the second
carrier-sensing threshold may be applied when detecting signals
originating from outside of the service set to which the
carrier-sensing communication unit belongs.
[0095] In other words, the proposed technology may thus, for
example, use the first carrier-sensing threshold for carrier
sensing with respect to transmissions identified as originating
from within a specific I/BSS and/or ESS, while using the second
carrier-sensing threshold for carrier sensing with respect to
transmissions identified as originating from other I/BSS:s and/or
other ESS:s.
[0096] By way of example, the second carrier-sensing threshold is
set to a higher level than the first carrier-sensing threshold.
[0097] For example, the second carrier-sensing threshold may be
aligned to a level used in the first wireless communication system
for energy detection.
[0098] As an example, the second carrier-sensing threshold may be
aligned to a level of a threshold used in a second, different
wireless communication system for determining whether the medium is
available for access.
[0099] In a particular embodiment, the second wireless
communication system is of a different type or radio access
technology than the first wireless communication system.
[0100] By way of example, the first wireless communication system
may be a Wireless Local Area Network, WLAN, system and the second
wireless communication system may be a cellular radio network
operating in unlicensed spectrum.
[0101] For example, the first wireless communication system may be
a Wi-Fi system.
[0102] For example, the second wireless communication system may be
based on License Assisted Access, LAA, or Long Term Evolution, LTE,
unlicensed.
[0103] The method may for example be performed by a communication
unit such as an access point or wireless communication device of
the first wireless communication system.
[0104] The proposed technology may also be regarded as a technology
for improving the coexistence between different types of wireless
communication systems operating in unlicensed spectrum.
[0105] It should also be understood that the proposed technology
may be applied on the network side and/or the terminal side.
[0106] The proposed technology may be used separately, or combined
and/or integrated with any conventional mechanism involving normal
carrier sensing thresholds.
[0107] For a better understanding of the proposed technology, it
may be useful with a brief overview and analysis with reference to
the particular non-limiting context of a Wireless Local Area
Network, WLAN.
[0108] The WLAN technology is a general technology for local
wireless communications. As the name implies Wireless Local Area
Network, WLAN, technology offers a basis for wireless
communications within a local area coverage. The WLAN technology
includes industry-specific solutions as well as proprietary
protocols, although most commercial applications are based on
well-accepted standards such as the various versions of IEEE
802.11, also popularly referred to as Wi-Fi.
[0109] WLAN is standardized in the IEEE 802.11 specifications such
as IEEE Standard for Information technology--Tele-communications
and information exchange between systems. Local and metropolitan
area networks--Specific requirements. Part 11: Wireless LAN Medium
Access Control (MAC) and Physical Layer (PHY) Specifications). WLAN
systems following the 802.11 MAC specifications operate based on
distributed medium or channel access, meaning that each node in the
network has more or less equal probability of accessing the
medium.
[0110] WLAN or Wi-Fi currently mainly operates on the 2.4 GHz or
the 5 GHz band. The IEEE 802.11 specifications regulate the access
points' or wireless terminals' physical layer, MAC layer, and other
aspects to secure compatibility and inter-operability between
access points, also referred to as APs, and wireless devices or
terminals, also referred to as STAs. Wi-Fi is generally operated in
unlicensed bands, and as such, communication over Wi-Fi may be
subject to interference sources from any number of both known and
unknown devices. Wi-Fi is commonly used as wireless extensions to
fixed broadband access, e.g., in domestic environments and
hotspots, like airports, train stations and restaurants.
[0111] The WLAN technology relies on Carrier Sensing Multiple
Access with Collision Avoidance, CSMA/CA, in order to effectively
and fairly share the wireless medium among different WLAN entities
and even different Radio Access Technologies, RATs. CSMA/CA applied
by the WLAN system demands that every device that wishes to send
data senses the common communication channel or medium before
carrying out a transmission in order to avoid duplicate
transmissions that usually would result in loss of data and need of
retransmissions. In order for a device to deem the channel busy, it
has to detect a transmission, the received signal strength level of
which surpasses a pre-determined threshold, referred to as a CCAT
threshold, as previously described in connection with FIG. 1.
[0112] With static CCAT, a node may refrain from accessing the
medium since it is exposed to concurrent transmissions in
neighboring Basic Serving Set, BSSs, although simultaneous or
concurrent communication would be possible. This limits the
performance of current systems, especially as the CCA threshold
used today is very low, -82 dBm. If STAs and APs could dynamically
adapt their carrier sensing threshold then the amount of concurrent
transmissions in the system may be increased without increasing the
probability of collisions within the BSS. This would mean an
increase in spectral efficiency of the system.
[0113] In a particular non-limiting example, it is proposed that
Wi-Fi nodes identify or detect if there is another wireless system
present in the same channel, e.g. an LTE-LAA system. If there are
ongoing LAA transmissions the access point, AP, may for example
broadcast to the STA's in the BSS that the COAT should be set to
the same level as the Energy Detect, ED, threshold normally used
for transmissions outside its own BSS. For transmissions within the
same BSS, e.g., if it is identified that a transmission originates
from a user communicating within own BSS, the channel could
preferably be considered as being busy to avoid collisions. In this
particular way, the channel will be shared with LAA in a way that
does not give LAA a large advantage.
[0114] Using the above-described method, Wi-Fi and LAA may compete
for transmission opportunities using the same definition of when a
channel is perceived as occupied. Within a BSS, it may be more
important to protect own traffic and thus, there may be no gain
using the same thresholds as for Energy Detect.
[0115] The above-described problem is best illustrated using three
different "entities" or access points using the same channel; AP1
and AP2 and LAA, for example referring to FIG. 4 and FIG. 5. For
the purpose of description, we assume that AP1 and AP2 are not part
of the same Extended/Basic Service Set, E/BSS. For example, AP1 and
AP2 are part of BSS1 and BSS2, respectively.
[0116] If AP 1 uses a first threshold level -82 dBm towards AP2 and
LAA uses a second threshold level -62 dBm towards AP2, LAA will
perceive transmission opportunities when AP1 perceive channel
busy.
[0117] If AP2 uses -82 dBm towards AP1 and LAA use -62 dBm towards
AP1, LAA will perceive transmission opportunities when AP2 perceive
channel busy.
[0118] To make the situation more equal in terms of assessing if
the channel is actually busy or not, it would be beneficial to use
the same threshold.
[0119] First, consider the situation in FIG. 4, where AP1 and AP2
are taking turns in accessing the channel. In FIG. 5, a base
station such as an LAA eNodeB, eNB, is added. The eNB will not
defer for AP2, but rather transmit concurrently. The AP1 may be
disadvantaged since it will time-share the channel with both the
eNB and AP2. What may be in particular problematic is that AP1 will
only find the channel idle if both AP2 and the eNB are not
transmitting. Since the eNB will not defer from AP2, it is easy to
see that AP2 can be almost starved. Suppose the load in BSS2
corresponding to AP2 is 75%. Furthermore, suppose that the load in
LAA is also 50%. If BSS2 and LAA are assumed to be independent of
one another, the probability that the channel is found to be idle
is (1-3/4)*1/2=12.5%. For some applications this will not be
sufficient.
[0120] In a particular example, it is suggested that AP1 should,
upon detection of the presence of the eNB, change its COAT to the
second threshold level, such as the ED level (-62 dBm), and hence
transmit concurrently with AP2. In this way the channel is shared
in a fair way with the LAA eNB. As the load in this example was 50%
for LAA, it will leave 50% of the channel time for BSS1. Thus LAA
will still have 50%, but the channel occupancy for BSS1 has
increased from 12.5% to 50%. Essentially, fair sharing has been
achieved between LAA and BSS1 at the same time as full spatial
reuse is achieved with BSS2.
[0121] Examples of how to Identify that a Network Node Using
Another Technology is Present
[0122] Signal Patterns
[0123] If a Wi-Fi node (AP or terminal) finds the medium busy
through energy detect more than X % of the time one may suspect
that another system is also using the same channel, where X is a
configurable value. The Wi-Fi node could then measure the duration
of these busy periods--and if the period is constant it may be
concluded that a frame based wireless system is also present in the
channel.
[0124] Explicitly Signaling
[0125] If e.g. the Wi-Fi node is co-located with the LAA node, in
the network node (AP and eNB) or in the device node, the Wi-Fi node
may obtain information about the LAA activity through explicit
(node-internal) signaling.
[0126] Spectrum Analysis/Estimation
[0127] Different signals have different spectral properties which
can be used to determine what standards are present. LTE, for
instance, has a bandwidth of 18 MHz, whereas 802.11ax is proposed
to have a signal bandwidth of more than 19 MHz, both systems
operating in a 20 MHz channel. By detecting the bandwidth of the
signals, it can thus be determined whether LAA is also operating in
the band in addition to Wi-Fi.
[0128] Time Correlation
[0129] Systems using OFDM uses a cyclic prefix (CP), also referred
to as guard interval (GI) to handle delay spread of the channel. As
the CP is just a copy of the last part of an OFDM symbol, this can
be used to determine the duration of an OFDM symbol. As the lengths
of the OFDM symbols are different for LAA and Wi-Fi, this is a
simple means to determine what systems are using the channel.
[0130] Examples of how to Share the Threshold Change
[0131] In case the AP identifies that another wireless system is
present in the same channel, the AP may inform the associated STAs
through broadcast messages that the COAT should be changed to the
level of ED. This may for instance be done in the beacon. However,
it may also be done using dedicated signaling to individual
STAs.
[0132] In case a terminal identifies that another wireless system
is present in the same channel it may inform the AP that this is
the case, and the AP in turn may broadcast this information, as
explained above.
[0133] It may also be a fully distributed scheme. For example,
since there may be a situation where only some of the STAs are
affected by the LAA activities, it may be preferred that the STAs
identify this autonomously without involving the AP, and then set
the COAT accordingly. This may effectively means that some STAs in
a BSS may use the first threshold level and others may use the
second threshold level. For example, some STAs may use COAT=-82
dBm, whereas others may use -62 dBm.
[0134] It will be appreciated that the methods and devices
described herein can be combined and re-arranged in a variety of
ways.
[0135] For example, embodiments may be implemented in hardware, or
in software for execution by suitable processing circuitry, or a
combination thereof.
[0136] The steps, functions, procedures, modules and/or blocks
described herein may be implemented in hardware using any
conventional technology, such as discrete circuit or integrated
circuit technology, including both general-purpose electronic
circuitry and application-specific circuitry.
[0137] Particular examples include one or more suitably configured
digital signal processors and other known electronic circuits, e.g.
discrete logic gates interconnected to perform a specialized
function, or Application Specific Integrated Circuits, ASICs.
[0138] Alternatively, at least some of the steps, functions,
procedures, modules and/or blocks described herein may be
implemented in software such as a computer program for execution by
suitable processing circuitry such as one or more processors or
processing units.
[0139] Examples of processing circuitry includes, but is not
limited to, one or more microprocessors, one or more Digital Signal
Processors, DSPs, one or more Central Processing Units, CPUs, video
acceleration hardware, and/or any suitable programmable logic
circuitry such as one or more Field Programmable Gate Arrays,
FPGAs, or one or more Programmable Logic Controllers, PLCs.
[0140] It should also be understood that it may be possible to
re-use the general processing capabilities of any conventional
device or unit in which the proposed technology is implemented. It
may also be possible to re-use existing software, e.g. by
reprogramming of the existing software or by adding new software
components.
[0141] According to another aspect, there is provided an
arrangement configured to control access to a shared wireless
medium in a first wireless communication system based on a
contention-based protocol for medium access involving carrier
sensing, wherein the first wireless communication system is of a
first radio access technology. The arrangement is configured to
determine whether a second wireless communication system of a
second, different radio access technology is operating on the same
channel of the shared wireless medium as the first wireless
communication system. The arrangement is also configured to
initiate, if the second wireless communication system is operating
on the same channel, a change of a carrier-sensing threshold used
in the first wireless communication system for determining, for at
least one communication unit, whether the medium is available for
access from a first level to a second, different level.
[0142] By way of example, the carrier-sensing threshold used in the
first wireless communication system for determining, for at least
one communication unit, whether the medium is available for access
is increased from a first lower level to a second higher level.
[0143] For example, the carrier-sensing threshold used in the first
wireless communication system for determining, for at least one
communication unit, whether the medium is available for access may
be aligned to a so-called co-existence threshold level which
differs from a default carrier-sensing threshold level used for
signal detection within the first wireless communication
system.
[0144] In a particular example, the default carrier-sensing
threshold level is nevertheless maintained for carrier-sensing
applicable for transmissions originating from users within the same
service set.
[0145] Typically, the co-existence threshold level corresponds to a
situation of co-existence of transmissions of the first wireless
communication system and the second wireless communication system
on the same channel.
[0146] As an example, the co-existence threshold level is higher
than the default carrier-sensing threshold level.
[0147] In a particular embodiment, the co-existence level
corresponds to the level of a threshold used in the second wireless
communication system for determining whether the medium is
available for access.
[0148] By way of example, the co-existence level may correspond to
the level used in the first wireless communication system for
determining whether the medium is available for access when no
carrier is detected.
[0149] The co-existence level may correspond to the level used in
the first wireless communication system for energy detection.
[0150] As an example, the carrier-sensing threshold is a threshold
for detection of signals within the first wireless communication
system.
[0151] By way of example, the first wireless communication system
may be a Wireless Local Area Network, WLAN, system and the second
wireless communication system may be a cellular radio network
operating in unlicensed spectrum.
[0152] For example, the first wireless communication system may be
a Wi-Fi system.
[0153] For example, the second wireless communication system may be
based on License Assisted Access, LAA, or Long Term Evolution, LTE,
unlicensed.
[0154] There is also provided an arrangement configured for carrier
sensing by a communication unit in a first wireless communication
system, wherein the communication unit belongs to a service set.
The arrangement is configured to assign a first carrier-sensing
threshold for use in the first wireless communication system,
applicable for transmissions identified as originating from within
the same service set. The arrangement is also configured to assign
a second carrier-sensing threshold for use in the first wireless
communication system, applicable for transmissions identified as
originating from other service sets, wherein the first
carrier-sensing threshold and the second carrier-sensing threshold
are different.
[0155] In particular, this means that the first carrier-sensing
threshold may be applied when detecting signals to/from
communication units within the service set to which the
carrier-sensing communication unit belongs, whereas the second
carrier-sensing threshold may be applied when detecting signals
originating from outside of the service set to which the
carrier-sensing communication unit belongs.
[0156] By way of example, the second carrier-sensing threshold is
set to a higher level than the first carrier-sensing threshold.
[0157] For example, the second carrier-sensing threshold may be
aligned to a level used in the first wireless communication system
for energy detection.
[0158] As an example, the second carrier-sensing threshold may be
aligned to a level of a threshold used in a second, different
wireless communication system for determining whether the medium is
available for access.
[0159] In a particular embodiment, the second wireless
communication system is of a different type or radio access
technology than the first wireless communication system.
[0160] By way of example, the first wireless communication system
may be a Wireless Local Area Network, WLAN, system and the second
wireless communication system may be a cellular radio network
operating in unlicensed spectrum.
[0161] For example, the first wireless communication system may be
a Wi-Fi system.
[0162] For example, the second wireless communication system may be
based on License Assisted Access, LAA, or Long Term Evolution, LTE,
unlicensed.
[0163] FIG. 6 is a schematic block diagram illustrating an example
of an arrangement according to an embodiment. In this particular
example, the arrangement 100 comprises a processor 110 and a memory
120, the memory comprising instructions executable by the
processor, whereby the arrangement is operative to perform the
above functions, steps and/or actions, including to control access
to the shared wireless medium, and to enable carrier sensing,
respectively.
[0164] Optionally, the arrangement 100 may also include a
communication circuit 130. The communication circuit may include
functions for wired and/or wireless communication with other
devices and/or network nodes in the network. In a particular
example, the communication circuit may be based on radio circuitry
for communication with one or more other nodes, including
transmitting and/or receiving information. The communication
circuit may be interconnected to the processor and/or memory.
[0165] According to yet another aspect, there is provided a
communication unit comprising an arrangement as described
herein.
[0166] FIG. 7 is a schematic diagram illustrating an example of a
communication unit comprising the arrangement of FIG. 6. The
communication unit 10 basically comprises the arrangement 100. The
communication unit 10 may for example be a network node such as an
access point, radio network node or access controller, or a
wireless communication device.
[0167] In case, the arrangement 100 itself does not include any
communication circuit for wired and/or wireless communication with
other devices and/or network nodes, the arrangement 100 may
alternatively use the communication functionality of the
communication unit 10 for external communication. In this case, the
arrangement 100 is connected to the communication circuit(s) (not
shown in FIG. 7) of the communication unit.
[0168] FIG. 8 is a schematic diagram illustrating an example of a
computer implementation according to an embodiment.
[0169] In this particular example, at least some of the steps,
functions, procedures, modules and/or blocks described herein are
implemented in a computer program 225; 235, which is loaded into
the memory 220 for execution by processing circuitry including one
or more processors. The processor(s) 210 and memory 220 are
interconnected to each other to enable normal software execution.
An optional input/output device may also be interconnected to the
processor(s) and/or the memory to enable input and/or output of
relevant data such as input parameter(s) and/or resulting output
parameter(s).
[0170] The term `processor` should be interpreted in a general
sense as any system or device capable of executing program code or
computer program instructions to perform a particular processing,
determining or computing task.
[0171] The processing circuitry including one or more processors is
thus configured to perform, when executing the computer program,
well-defined processing tasks such as those described herein.
[0172] The processing circuitry does not have to be dedicated to
only execute the above-described steps, functions, procedure and/or
blocks, but may also execute other tasks.
[0173] According to still another aspect, there is provided a
computer program for controlling, when executed by at least one
processor, access to a shared wireless medium in a first wireless
communication system based on a contention-based protocol for
medium access involving carrier sensing, wherein the first wireless
communication system is of a first radio access technology. The
computer program comprises instructions, which when executed, cause
the at least one processor to: [0174] determine whether a second
wireless communication system of a second, different radio access
technology is operating on the same channel of the shared wireless
medium as the first wireless communication system; and [0175]
initiate, if the second wireless communication system is operating
on the same channel, a change of a carrier-sensing threshold used
in the first wireless communication system for determining, for at
least one communication unit, whether the medium is available for
access from a first level to a second, different level.
[0176] There is also provided a computer program for performing,
when executed by at least one processor, threshold assignment for
carrier sensing in a first wireless communication system. The
computer program comprises instructions, which when executed, cause
the at least one processor to: [0177] assign a first
carrier-sensing threshold for use in the first wireless
communication system, applicable for transmissions identified as
originating from within the same service set as the communication
unit performing the carrier-sensing; [0178] assign a second,
different carrier-sensing threshold for use in the first wireless
communication system, applicable for transmissions identified as
originating from other service sets.
[0179] The proposed technology also provides a carrier comprising
the computer program, wherein the carrier is one of an electronic
signal, an optical signal, an electromagnetic signal, a magnetic
signal, an electric signal, a radio signal, a microwave signal, or
a computer-readable storage medium.
[0180] According to another aspect, there is thus provided a
computer-program product comprising a computer-readable medium
having stored thereon a computer program as defined herein.
[0181] By way of example, the software or computer program 225; 235
may be realized as a computer program product, which is normally
carried or stored on a computer-readable medium 220; 230, in
particular a non-volatile medium. The computer-readable medium may
include one or more removable or non-removable memory devices
including, but not limited to a Read-Only Memory, ROM, a Random
Access Memory, RAM, a Compact Disc, CD, a Digital Versatile Disc,
DVD, a Blu-ray disc, a Universal Serial Bus, USB, memory, a Hard
Disk Drive, HDD, storage device, a flash memory, a magnetic tape,
or any other conventional memory device. The computer program may
thus be loaded into the operating memory of a computer or
equivalent processing device for execution by the processing
circuitry thereof.
[0182] The flow diagram or diagrams presented herein may therefore
be regarded as a computer flow diagram or diagrams, when performed
by one or more processors. A corresponding apparatus may be defined
as a group of function modules, where each step performed by the
processor corresponds to a function module. In this case, the
function modules are implemented as a computer program running on
the processor. Hence, the arrangement may alternatively be defined
as a group of function modules, where the function modules are
implemented as a computer program running on at least one
processor.
[0183] The computer program residing in memory may thus be
organized as appropriate function modules configured to perform,
when executed by the processor, at least part of the steps and/or
tasks described herein.
[0184] FIG. 9 is a schematic diagram illustrating an example of an
apparatus for controlling access to a shared wireless medium in a
wireless communication system according to an embodiment.
[0185] According to yet another aspect, there is provided an
apparatus 300 for controlling access to a shared wireless medium in
a first wireless communication system based on a contention-based
protocol for medium access involving carrier sensing, wherein the
first wireless communication system is of a first radio access
technology. The apparatus 300 comprises: [0186] a determining
module 310 for determining whether a second wireless communication
system of a second, different radio access technology is operating
on the same channel of the shared wireless medium as the first
wireless communication system; and [0187] a control module 320 for
initiating, if the second wireless communication system is
operating on the same channel, a change of a carrier-sensing
threshold used in the first wireless communication system for
determining, for at least one communication unit, whether the
medium is available for access from a first level to a second,
different level.
[0188] FIG. 10 is a schematic diagram illustrating an example of an
apparatus for threshold assignment for carrier sensing in a
wireless communication system according to an embodiment.
[0189] There is also provided an apparatus for threshold assignment
for carrier sensing in a first wireless communication system. The
apparatus comprises: [0190] a module 410 for assigning a first
carrier-sensing threshold for use in the first wireless
communication system, applicable for transmissions identified as
originating from within the same service set as the communication
unit performing the carrier-sensing; and [0191] a module 420 for
assigning a second carrier-sensing threshold for use in the first
wireless communication system, applicable for transmissions
identified as originating from other service sets, [0192] wherein
the first carrier-sensing threshold and the second carrier-sensing
threshold are different.
[0193] The module 410 and the module 420 may also be referred to as
a first assigning module 410 and a second assigning module 420.
Alternatively, the module 410 and the module 420 are integrated
into a common assigning module.
[0194] Alternatively it is possibly to realize the modules in FIG.
9 and FIG. 10, respectively, predominantly by hardware modules, or
alternatively by hardware, with suitable interconnections between
relevant modules. Particular examples include one or more suitably
configured digital signal processors and other known electronic
circuits, e.g. discrete logic gates interconnected to perform a
specialized function, and/or Application Specific Integrated
Circuits, ASICs, as previously mentioned. Other examples of usable
hardware include input/output, I/O, circuitry and/or circuitry for
receiving and/or sending signals. The extent of software versus
hardware is purely an implementation selection.
[0195] The embodiments described above are merely given as
examples, and it should be understood that the proposed technology
is not limited thereto. It will be understood by those skilled in
the art that various modifications, combinations and changes may be
made to the embodiments without departing from the present scope as
defined by the appended claims. In particular, different part
solutions in the different embodiments can be combined in other
configurations, where technically possible.
* * * * *